Light emitting device

ABSTRACT

A light emitting device includes a package having a recess, a light emitting element disposed in the recess, a translucent sealing material provided in the recess to encapsulate the light emitting element, and a film provided on the translucent sealing material. The film has a contact surface to contact the translucent sealing material and an outer surface opposite to the contact surface. The film includes a translucent base material and two or more layers of particles stacked in the translucent base material between the contact surface and the outer surface. At least one of the particles is exposed in a vicinity of the outer surface of the film.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of the U.S. patentapplication Ser. No. 15/853,962 filed Dec. 26, 2017, which claimspriority under 35 U. S. C. § 119 to Japanese Patent Application No.2016-254332 filed on Dec. 27, 2016, the contents of these applicationsare hereby incorporated herein by reference in their entirety.

BACKGROUND Technical Field

This disclosure relates to a light emitting device.

Description of Background

Light emitting diodes (LEDs) are used in various applications includinglighting devices, backlights for liquid crystal displays used inpersonal computers (PCs) and televisions, large displays, and so forth.LED light sources are facing an increase in demand for the variousapplications as mentioned above as well as an increasing need forimproving light output therefrom. For example, Japanese UnexaminedPatent Application Publication No. 2003-086846 discloses a lightemitting device in which a film containing a light diffusion member isformed on an upper surface of a sealing resin of the light emittingdevice.

SUMMARY OF INVENTION

According to an embodiment of the present disclosure, a light emittingdevice includes a package having a recess, a light emitting elementdisposed in the recess, a translucent sealing material provided in therecess to encapsulate the light emitting element, and a film provided onthe translucent sealing material. The film has a contact surface tocontact the translucent sealing material and an outer surface oppositeto the contact surface. The film includes a translucent base materialand two or more layers of particles stacked in the translucent basematerial between the contact surface and the outer surface. At least oneof the particles is exposed in a vicinity of the outer surface of thefilm.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1 is a schematic perspective view illustrating a constitution of alight emitting device according to a first embodiment.

FIG. 2 is a schematic plan view illustrating the constitution of thelight emitting device according to the first embodiment.

FIG. 3 is a schematic cross-sectional view illustrating the constitutionof the light emitting device according to the first embodiment, whichshows a cross section taken along the III-III line in FIG. 2.

FIG. 4 is a flowchart illustrating procedures of a method formanufacturing the light emitting device according to the firstembodiment.

FIG. 5 is a schematic cross-sectional view illustrating a constitutionof a package prepared in a package preparation step of the method formanufacturing the light emitting device according to the firstembodiment.

FIG. 6 is a schematic cross-sectional view illustrating a light emittingelement mounting step of the method for manufacturing the light emittingdevice according to the first embodiment.

FIG. 7 is a schematic cross-sectional view illustrating a sealing memberforming step of the method for manufacturing the light emitting deviceaccording to the first embodiment.

FIG. 8 is a schematic cross-sectional view illustrating a film formingstep of the method for manufacturing the light emitting device accordingto the first embodiment.

FIG. 9 is a schematic cross-sectional view illustrating anabrasive-blasting step of the method for manufacturing the lightemitting device according to the first embodiment.

FIG. 10A is a schematic plan view of a first example of a direction inwhich an abrasive material is jetted in the abrasive-blasting step inthe method for manufacturing the light emitting device according to thefirst embodiment.

FIG. 10B is a schematic plan view of a second example of directions inwhich the abrasive material is jetted in the abrasive-blasting step inthe method for manufacturing the light emitting device according to thefirst embodiment.

FIG. 10C is a schematic plan view of a third example of directions inwhich the abrasive material is jetted in the abrasive-blasting step inthe method for manufacturing the light emitting device according to thefirst embodiment.

FIG. 11A is a schematic cross-sectional view illustrating a firstsubstep in the abrasive-blasting step in the method for manufacturingthe light emitting device according to the first embodiment.

FIG. 11B is a schematic cross-sectional view illustrating a secondsubstep in the abrasive-blasting step in the method for manufacturingthe light emitting device according to the first embodiment.

FIG. 12 is a schematic cross-sectional view illustrating a constitutionof a light emitting device according to a second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

Light emitting devices and methods for manufacturing the light emittingdevices according to embodiments will be described below. Note thatdrawings used for reference in the following description schematicallyillustrate this embodiment. For this reason, scales, intervals,positional relations, and the like of components may be exaggerated orillustration of some of the components may be omitted. Moreover, in thefollowing description, the components having the same names or denotedby the same reference numerals represent the same or similar componentsin principle, and detailed explanations thereof will be omitted asappropriate.

First Embodiment Constitution of Light Emitting Device

A constitution of a light emitting device according to a firstembodiment will be described below with reference to FIG. 1 to FIG. 3.

FIG. 1 is a schematic perspective view illustrating the constitution ofa light emitting device according to a first embodiment. FIG. 2 is aschematic plan view illustrating the constitution of the light emittingdevice according to the first embodiment. FIG. 3 is a schematiccross-sectional view illustrating the constitution of the light emittingdevice according to the first embodiment, which shows a cross sectiontaken along the III-III line in FIG. 2.

Note that hatching in FIG. 1 indicates the presence of a film 6 in afirst recess 2 a. In the meantime, FIG. 1 and FIG. 2 illustratecomponents in the first recess 2 a, which are seen through thetranslucent film 6 and a translucent sealing member (a translucentsealing material) 5 disposed below the film 6, respectively.

A light emitting device 100 according to the first embodiment includes:a package 2 having a substantially square shape in a plan view andincluding the first recess 2 a which is opened to an upper surface side;a light emitting element 1 mounted in the first recess 2 a; the sealingmember 5 disposed in the first recess 2 a and encapsulating the lightemitting element 1; and the film 6 formed on the sealing member 5. Thefilm 6 is provided with multiple projections that are formed byparticles 62 contained in a base material 61 of the film 6. Meanwhile,the package 2 includes lead electrodes 3 and a light shielding member 4.

The light emitting element 1 is die-bonded onto a lead electrode 31disposed on a bottom surface 2 b of the first recess 2 a. An anodeelectrode being one of electrodes of the light emitting element 1 iselectrically connected to a lead electrode 32 by using a wire 7. Acathode electrode being another electrode of the light emitting element1 is electrically connected to the lead electrode 31 by using anotherwire 7.

As for an emission color of the light emitting element 1, a color of anywavelength can be selected depending on the usage. The light emittingelement 1 that emits blue light or green light may preferably employ alight emitting element made of nitride semiconductor expressed byIn_(X)Al_(Y)Ga_(1-X-Y)N (0≤X≤1, 1≤Y≤1, X+Y≤1), which has an emissionwavelength in a range of near-ultraviolet light to visible light.

A protection element 8 is mounted in the first recess 2 a of the lightemitting device 100. Here, the protection element 8 is a Zener diode,for example.

The first recess 2 a of the package 2 is a region for mounting the lightemitting element 1. The bottom surface 2 b of the first recess 2 a isformed of the lead electrodes 3 and the light shielding member 4. Sidewalls of the first recess 2 a are formed of the light shielding member4. A lower surface of the package 2 is a flat surface and is designed toexpose the lead electrodes 3. This lower surface constitutes a mountingsurface of the light emitting device 100.

The lead electrodes 3 include the lead electrode 31 and the leadelectrode 32 each in a flat plate shape, which are provided separatelyfrom each other at the bottom of the package 2. Part of upper surfacesof the lead electrodes 31 and 32 constitute the bottom surface 2 b ofthe first recess 2 a. Here, the one electrode of the protection element8 provided on the lower surface side is die-bonded and thus electricallyconnected to the lead electrode 32, and the other electrode thereofprovided on the upper surface side is electrically connected to the leadelectrode 31 through the wire 7.

For example, a Cu-based alloy is used as a material of the leadelectrodes 3.

The upper surfaces of the lead electrodes 3 constituting the bottomsurface 2 b of the first recess 2 a may be plated with Ag, Au, Ni, orthe like in order to improve light reflectivity and/or adhesion to thewire 7, a die-bonding member, and the like.

The light shielding member 4 is a member designed to fix the two leadelectrodes 31 and 32 separately from each other and to constitute theside walls of the first recess 2 a. The light shielding member 4 isformed of a material that shields light while inhibiting transmission ofthe light, and either a light reflective material designed to shieldlight by reflecting the light or a light absorptive material designed toshield light by absorbing the light is used therein.

Examples of a resin used for a matrix of the light shielding member 4include thermoplastic resins and thermosetting resins.

Examples of thermoplastic resins include polyphthalamide resin, liquidcrystal polymers, poly butylene terephthalate (PBT), and unsaturatedpolyesters.

Examples of thermosetting resins include epoxy resins, modified epoxyresins, silicone resins, and modified silicone resins.

In regard to the light shielding member 4 having light reflectiveproperties, the light shielding member 4 can be formed of a resinmaterial to which light reflective properties are imparted byincorporating a light reflective substance in the matrix. Examples ofthe light reflective substance include TiO₂, Al₂O₃, ZrO₂, MgO, and thelike.

In regard to the light shielding member 4 having light absorbingproperties, the light shielding member 4 can be formed of a resinmaterial to which light absorbing properties are imparted byincorporating a light absorptive substance in the matrix. A blackpigment may be an example of the light absorptive substance. To be moreprecise, examples of the black pigment include carbon black, graphite,and the like.

The sealing member 5 is provided in the first recess 2 a of the package2, and encapsulates the light emitting element 1 and the protectionelement 8. A filling amount of a resin constituting the sealing member 5only needs to be set to a sufficient amount for covering electroniccomponents such as the light emitting element 1 as well as the wires 7and the like. In order to minimize the filling amount of this material,the sealing member 5 may have a second recess (a substantially curvedconcave shape). The second recess has a substantially curved form incross-sectional view passing through an optical axis of the lightemitting element 1. The light emitting element 1 is disposed immediatelybelow a portion in a vicinity of a center of the second recess of thesealing member 5. Note that the surface of the sealing member 5 may beformed into a flat shape instead of providing the second recess.Meanwhile, when a lens function is imparted to the sealing member 5, thesealing member 5 may be formed into a bullet shape or a convex lensshape by raising the surface of the sealing member 5.

A translucent thermosetting resin can be used as a resin constitutingthe sealing member 5. Examples of the thermosetting resin include asilicone resin, an epoxy resin, a urea resin, and the like. In additionto the above-mentioned materials (base materials), the sealing member 5may also contain a wavelength conversion substance, the above-describedlight reflective substance, and the like in order to provide certainfunctions thereto.

The sealing member 5 may also contain particles of the light absorptivesubstance such as carbon black as another filler to the extent notdamaging the translucency. In this way, it is possible to improve alight distribution characteristic of light emitted from the lightemitting device 100.

The wavelength conversion substance is disposed mainly around the lightemitting element 1 and in the vicinity of the bottom surface 2 b of thefirst recess 2 a. The wavelength conversion substance is a phosphorwhich performs wavelength conversion by absorbing part or all of thelight from the light emitting element 1 and emitting light at adifferent wavelength. For example, it is possible to produce white lightby combining the light emitting element 1 that emits blue light with thewavelength conversion substance that absorbs the blue light and emitsyellow light. The wavelength conversion substance preferably has largerspecific gravity than that of the uncured base material of the sealingmember 5 at the time of manufacture.

Examples of the wavelength conversion substance include: yellowphosphors such as YAG phosphor expressed by Y₃Al₅O₁₂:Ce and a silicate;and red phosphors such as CASN phosphor expressed by CaAlSiN₃:Eu and KSFphosphor expressed by K₂SiF₆:Mn.

The film 6 contains the particles 62 as a filler for adjusting viscosityof the uncured resin at the time of formation by using the translucentresin as the base material 61, and for imparting light diffuseness tothe film 6. In the meantime, at least part of the particles 62 arepartially exposed from the base material 61, and an upper surface (anouter surface) of the film 6 is thus provided with multiple projectionsoriginating from the particles 62.

A translucent thermosetting resin can be used as the base material 61 ofthe film 6. Examples of the thermosetting resin include silicone resin,epoxy resin, urea resin, and the like.

A material having a lower refractive index than that of the basematerial 61 is used for the particles 62. Specifically, the particles 62may be formed of silica (SiO₂), for example. When silicone resin havingthe refractive index of 1.52 is used as the base material 61, forexample, it is possible to employ SiO₂ having the refractive index of1.46 as the particles 62.

Grain sizes of the particles 62 are preferably set in a range from about0.5 micrometer (μm) to 12.5 micrometer (μm) inclusive. By setting thegrain sizes of the particles 62 within this range, it is possible toefficiently reduce regular reflection light components of external lighton the upper surface of the film 6 by using the multiple projectionsformed originating from the particles 62.

Note that values of grain sizes of various fillers, abrasive materials,and the like in this specification are in accordance with an airpermeability method or Fisher-SubSieve-Sizers-No. (F. S. S. S. method)unless otherwise specified.

A density of the particles 62 in the film 6 is high. The area occupiedby the particles 62 therein is in a range of 2% to 20%, or preferably ina range of 3% to 10%, or more preferably in a range of 4% to 8%. Thisdensity corresponds to a case of measuring the area of 1 mm² in avicinity of the center of the first recess 2 a in a plan view.

By exposing the particles 62 having the lower refractive index than thatof the base material 61 on the upper surface of the film 6 serving as alight extraction plane of the light emitting device 100, it is possibleto reduce a difference in refractive index between the film 6 and theair (with the refractive index of 1.0) that serves as a medium at adestination of the extracted light. With the difference in refractiveindex equal to 0.03 or more than between the base material 61 and theparticles 62 in the film 6, it is possible to improve light extractionefficiency of the light emitting device 100 as a consequence of exposingthe particles 62.

The provision of the multiple projections on the upper surface of thefilm 6 establishes point contact of the upper surface with anothercomponent as the contact arises. Thus, it is possible to prevent theother component in contact from tacking (adhesion), and to facilitatehandling of the light emitting device 100 during manufacturing andmounting procedures.

The multiple projections on the upper surface of the film 6 can beformed by abrasive-blasting the upper surface of the film 6 to expose atleast part of the particles 62 partially from the base material 61. Inother words, the multiple projections on the upper surface of the film 6are preferably formed originating from the particles 62.

The regular reflection light components of the external light reflectedfrom the upper surface of the film 6 can be favorably reduced by themultiple projections formed originating from the particles 62 having thegrain sizes in the aforementioned range.

In the film 6, the density of the particles 62 to be disposed in thevicinity of the center of the second recess of the sealing member 5 ishigher than the density of the particles 62 to be disposed in aperiphery portion of the second recess of the sealing member 5. Here,the light emitting element 1 is disposed immediately below the portionin the vicinity of the center of the second recess of the sealing member5. Accordingly, it is possible to improve the light diffuseness and thereflectivity by setting the density of the particles 62 disposedimmediately above the light emitting element 1 higher than the densityof the particles 62 disposed in the periphery portion of the secondrecess of the sealing member 5.

The surface tackiness of the light emitting device is thought to behighest at the portion in the vicinity of the center of the uppersurface of the light emitting device. Therefore, it is possible toreduce the surface tackiness by increasing the density of the particles62 to be disposed in the vicinity of the center of the second recess ofthe sealing member 5 more than the density of the particles 62 to bedisposed in the periphery portion of the second recess of the sealingmember 5.

Since the multiple projections on the upper surface of the film 6 can beformed by abrasive-blasting the upper surface of the film 6 to expose atleast part of the particles 62 partially from the base material 61, anamount of grinding the portion in the vicinity of the center of thesecond recess of the sealing member 5 and an amount of grinding theportion in the periphery portion of the second recess of the sealingmember 5 can be equalized easily. For this reason, the film 6 has acharacteristic that a ratio of exposure of the particles 62 disposed inthe vicinity of the center of the second recess of the sealing member 5is substantially equal to a ratio of exposure of the particles 62disposed in the periphery portion of the second recess of the sealingmember 5.

Each wire 7 is a line to electrically connect the electronic componentsuch as the light emitting element 1 and the protection element 8 to thelead electrode 31 or 32. Examples of the material of the wires 7 includemetals such as Au, Ag, Cu, Pt, and Al, and alloys thereof. Inparticular, it is preferable to use Au for its excellence in heatconductivity and other factors.

Operation of Light Emitting Device

Next, an operation of the light emitting device 100 will be describedwith reference to FIG. 3. Note that the following description is basedon an assumption that the upper surface of the film 6 serving as thelight extraction plane of the light emitting device 100 is in contactwith the air.

The light emitting element 1 emits the light as a consequence ofconnecting an external power source to the lead electrodes 31 and 32.The light from the light emitting element 1 propagates in the sealingmember 5. Part or all of the light from the light emitting element 1undergoes the wavelength conversion by the wavelength conversionsubstance, then advances either directly or through reflection from thebottom surface and inner side surfaces of the first recess 2 a, and getstaken out of the upper surface of the film 6 to the outside. On theupper surface of the film 6, the light from the light emitting element 1is taken out to the outside partially through an interface between thebase material 61 and the air. Meanwhile, at a portion where any of theparticles 62 is disposed in the vicinity of the upper surface of thefilm 6, the light from the light emitting element 1 is taken out to theoutside through an interface between the particle 62 and the air. Thelight that passes through the interface between the particle 62 and theair can reduce more light reflection on the interface with the air thandoes the light that passes through the interface between the basematerial 61 and the air. As a consequence, it is possible to improvelight extraction efficiency of the light emitting device 100.

Meanwhile, when the light propagates from a medium having a relativelyhigher refractive index to a medium having a lower refractive index, thelight is totally reflected from an interface based on the Snell's law.An amount of light totally reflected from the interface can be reducedby diminishing the difference in refractive index on the interfacebetween the film 6 and the air. That is to say, the extractionefficiency of the light to the outside can be improved from theviewpoint of reduction in the total reflection as well.

Moreover, it is possible to bring the light into diffuse reflection byproviding the upper surface of the film 6 with the projectionsoriginating from the grain sizes of the particles 62. In other words,the regular reflection light components can be reduced. For this reason,it is possible to reduce deterioration in contrast of brightness of thelight emitted from the light emitting device 100 when observed in thedirection of regular reflection of the external light.

Manufacturing Method for Light Emitting Device

Next, a manufacturing method for a light emitting device according tothe first embodiment will be described with reference to FIG. 4 to FIG.11B.

FIG. 4 is a flowchart illustrating procedures of the method formanufacturing the light emitting device according to the firstembodiment. FIG. 5 is a schematic cross-sectional view illustrating aconstitution of a package prepared in a package preparation step of themethod for manufacturing the light emitting device according to thefirst embodiment. FIG. 6 is a schematic cross-sectional viewillustrating a light emitting element mounting step of the method formanufacturing the light emitting device according to the firstembodiment. FIG. 7 is a schematic cross-sectional view illustrating asealing member forming step of the method for manufacturing the lightemitting device according to the first embodiment. FIG. 8 is a schematiccross-sectional view illustrating a film forming step of the method formanufacturing the light emitting device according to the firstembodiment. FIG. 9 is a schematic cross-sectional view illustrating anabrasive-blasting step of the method for manufacturing the lightemitting device according to the first embodiment. FIG. 10A is aschematic plan view of a first example of a direction in which anabrasive material is jetted in the abrasive-blasting step in the methodfor manufacturing the light emitting device according to the firstembodiment. FIG. 10B is a schematic plan view of a second example ofdirections in which the abrasive material is jetted in theabrasive-blasting step in the method for manufacturing the lightemitting device according to the first embodiment. FIG. 10C is aschematic plan view of a third example of directions in which theabrasive material is jetted in the abrasive-blasting step in the methodfor manufacturing the light emitting device according to the firstembodiment. FIG. 11A is a schematic cross-sectional view illustrating afirst substep in the abrasive-blasting step in the method formanufacturing the light emitting device according to the firstembodiment. FIG. 11B is a schematic cross-sectional view illustrating asecond substep in the abrasive-blasting step in the method formanufacturing the light emitting device according to the firstembodiment.

The method for manufacturing the light emitting device 100 according tothe first embodiment includes a package preparation step S11, a lightemitting element mounting step S12, a sealing member forming step S13, afilm forming step S14, and an abrasive-blasting step S15.

The package preparation step S11 is a step of preparing the package 2including the lead electrodes 3 disposed on the bottom surface 2 b, andthe first recess 2 a opened upward while being surrounded by the lightshielding member 4 serving as the side walls.

First, a lead frame provided with external forms of the lead electrodes3 is formed by pressing and blanking a metal plate. Next, the lead frameis sandwiched between upper and lower molds provided with a cavitycorresponding to the shape of the light shielding member 4. Next, aresin material is injected into the cavity inside the molds and theresin material is taken out after being solidified or cured. Thus, thepackage 2 is prepared in which the light shielding member 4 is formedintegrally with the lead electrodes 3.

The light emitting element mounting step S12 is a step of mounting thelight emitting element 1 in the first recess 2 a of the package 2. Thelight emitting element 1 is die-bonded onto the lead electrode 31, andeach light emitting element 1 is electrically connected to thecorresponding lead electrodes 31 and 32 by using the wires 7. Here, theprotection element 8 is also mounted in the first recess 2 a.

The sealing member forming step S13 is a step of forming the sealingmember 5 in the first recess 2 a. First, the material of the sealingmember prepared so as to contain the wavelength conversion substance issupplied to the first recess 2 a in accordance with a potting methodusing a dispenser, for example. Next, the resin material is cured byheating with a heating apparatus such as a heater and a reflow furnace.The sealing member 5 is formed accordingly.

The film forming step S14 is a step of forming the film 6 on the sealingmember 5. First, a resin material containing the particles 62 in anuncured translucent resin intended to be the base material 61 issupplied onto the sealing member 5 in the first recess 2 a in accordancewith the potting method, for example. Next, the resin material is curedby heating. The film 6 is formed accordingly. At this time, theparticles 62 disposed in the vicinity of the upper surface of the film 6are covered with the base material 61.

The abrasive-blasting step S15 is a step of roughening the upper surfaceof the film 6 to the abrasive-blasting. The abrasive-blasting partiallyexposes at least part of the particles 62 disposed in the vicinity ofthe upper surface of the film 6, thereby forming the projectionsoriginating from the particles 62 on the upper surface of the film 6.

After the abrasive-blasting, a thickness of the film 6 is equal to ⅗ ofthe grain sizes of the particles 62 or more than, or preferably equal to¾ thereof or more than, or more preferably equal to ⅘ thereof or morethan. In other words, on the upper surface of the film 6, ⅖ or less ofwhole sizes of the particles 62 are exposed, or preferably ¼ or lessthereof are exposed, or more preferably ⅕ or less thereof are exposed.This film thickness is preferably measured in the vicinity of the centerof the first recess 2 a in a plan view.

The upper surface of the film 6 is finely roughened by performing theabrasive-blasting in such a way as to expose at least part of theparticles 62. Thus, the light diffuseness of the upper surface of thefilm 6 is improved and it is thus possible to obtain an antireflectioneffect on the upper surface of the film 6. Meanwhile, it is possible toreduce the surface tackiness of the upper surface of the light emittingdevice 100 by setting the exposure ratio of the particles 62 on thesurface of the film 6 within the aforementioned range. In addition, theparticles 62 can be suitably prevented from falling off the film 6 dueto the abrasive-blasting.

The abrasive-blasting is preferably conducted in accordance with a wetblasting method, which is carried out by jetting a slurry formed ofpurified water containing an abrasive material 92 from a nozzle 91 ontoa machining target surface, for example. The wet blasting method canreduce impact of the abrasive material 92 on a machining target objectas compared to a dry blasting method. Accordingly, the relatively softbase material 61 (the resin material) can be selectively ground off andremoved without significantly damaging the particles 62 in the film 6.

Moreover, the abrasive material 92 in smaller diameters can be used inthe wet blasting method, and this method is therefore suitable for finemachining. Accordingly, it is possible to remove portions of the basematerial 61 covering top surfaces of the particles 62 without formingrough bumps on the upper surface of the film 6. This makes it possibleto partially expose at least part of the particles 62 to the uppersurface of the film 6 and thus to form the projections originating fromthe particles 62.

At the time of removing the base material 61 covering the upper parts ofthe particles 62 in the vicinity of the upper surface of the film 6, itis preferable to conduct the abrasive-blasting in such a way as tominimize the detachment of the particles 62 from the base material 61.The grain sizes of the abrasive material 92 are set preferably in arange from about 3 μm to 14 μm inclusive. Here, the use of the abrasivematerial 92 with small grain sizes of about 3 μm is particularlypreferable because such an abrasive material is less likely to causescratches on the film 6. Meanwhile, when the slurry formed of thepurified water containing the abrasive material 92 is used in accordancewith the wet blasting method, the content of the abrasive material 92 inthe slurry is preferably set in a range from about 5% by volume to 30%by volume inclusive.

The abrasive material 92 preferably has higher hardness than that of thebase material 61 of the film 6, and materials such as alumina (Al₂O₃),silicon carbide (SiC), stainless steel, zirconia (ZrO₂), and glass areapplicable thereto.

A blast angle 91 a of the slurry containing the abrasive material 92 isset preferably in a range from 15 degrees to 45 degrees inclusive ormore preferably near 30 degrees with respect to the upper surface of thefilm 6 being the machining target surface.

If the abrasive material 92 is jetted onto the machining target surfaceat the blast angle 91 a close to the right angle (90°), the abrasivematerial 92 may easily stick into the base material 61 and remain in thepackage 2 after the abrasive-blasting. If the abrasive material 92 isjetted onto the machining target surface at the blast angle 91 a closeto a horizontal angle, the efficiency of removing the base material 61with the abrasive material 92 may be reduced. Therefore, by setting theblast angle 91 a within the aforementioned range, it is possible toefficiently remove the base material 61 and thus to expose the particles62 easily.

In the wet blasting method, the above-described slurry and compressedair are sprayed from the nozzle 91 of a blast gun toward the machiningtarget surface. An optimum value of a pressure of the compressed air (agun pressure of the blast gun) at this time varies with the shape andthe blast angle 91 a of the nozzle 91, the material, shape, and grainsizes of the abrasive material 92, and the like. Here, the pressure maybe set in a range of about 0.1 MPa to 0.5 MPa, for example.

A direction to jet the abrasive material 92 at the above-described blastangle 91 a may be set as appropriate depending on the purpose and theusage. In the case of an outdoor display or the like which uses thelight emitting device 100 as each pixel, for example, the light emittingdevice 100 may be required only to suppress a gloss in one direction. Inthis case, the slurry may be jetted only in one direction D1 in a planview.

When aiming at suppressing glosses in both directions, it is preferableto jet the abrasive material 92 in the direction D1 and then to jet theabrasive material 92 also in an opposite direction D2 (right side inFIG. 11B) by changing the orientation of the nozzle 9.

Furthermore, the abrasive material 92 may also be jetted also indirections D3 and D4 which are perpendicular to the directions D1 and D2in a plan view. Alternatively, the abrasive material 92 may be jetted inthree directions which are different by 120° from one another in a planview, for example.

Here, when the abrasive material 92 is jetted in multiple directions,one process in one direction is conducted on the entire upper surface ofthe film 6 and then another process is conducted while sequentiallychanging the orientation of the nozzle 91. In the meantime, theorientation of the nozzle 91 may be changed relatively to the lightemitting device 100. Hence, the orientation of the light emitting device100 may be changed while the nozzle 91 is fixed.

The light emitting device 100 is manufactured by carrying out therespective steps as described above.

In the manufacturing method for a light emitting device of thisembodiment, in the abrasive blasting, the slurry is jetted onto theupper surface of the film 6 which contains the particles 62.Accordingly, the relatively hard particles 62 remain intact in the film6 while only the surrounding portion of base material 61 is graduallyground off, and a difference in height is thus created between theparticles 62 and the base material 61. As a consequence, the lightemitting device 100 is provided with the multiple projections on theupper surface side, and thus reduces the regular reflection lightcomponents of the external light. For this reason, a display using thelight emitting device 100 as each pixel exerts an antireflection effect,which makes it possible to reduce the influence of the external lightand to favorably recognize the brightness and hue of the pixelirrespective of the direction of observation. Moreover, the lightemitting device 100 can also exert a tackiness prevention effect sincethe particles 62 are exposed from the film 6 to the air.

Second Embodiment

FIG. 12 is a schematic cross-sectional view illustrating a constitutionof the light emitting device according to the second embodiment. Also,FIG. 12 is the schematic cross-sectional view corresponding to the crosssection taken along the line in FIG. 2. A light emitting device 100Baccording to the second embodiment includes: the package 2; the lightemitting element 1 mounted on the package 2; the sealing member 5encapsulating the light emitting element 1; and a film 6B formed on thesealing member 5. This light emitting device 100B is different from thelight emitting device 100 according to the first embodiment in that twoor more layers of the particles 62 are stacked in the translucent basematerial 61 of the film 6B. In the following, the same constituents asthose in the light emitting device 100 according to the first embodimentwill be denoted by the same reference numerals and explanations thereofwill be omitted.

In the light emitting device 100B, the sealing member 5 has a secondrecess. The second recess has a substantially curved form incross-sectional view passing through the optical axis of the lightemitting element 1. A height required for flattening the second recessof the sealing member 5 is in a range of 10 μm to 15 μm, for example. Inthe light emitting device 100B, a resin material containing theparticles 62 in an uncured translucent resin intended to be the basematerial 61 is supplied in accordance with the potting method, forexample, so as to flatten the second recess of the sealing member 5 inthe first recess 2 a, for instance. In this case, the adjacent particles62 are stacked on one another, thereby forming two or more layers in thecase of using the particles 62 with grain sizes in a range of 3 μm to 5μm, for example. Meanwhile, the area occupied by the particles 62 isgreater than the area occupied by the base material 61 in a plan view ofthe film 6B. Specifically, the particles 62 are disposed so densely in aplan view of the film 6B that particles of the abrasive material 92contained in the slurry used in the abrasive-blasting do not reach theparticles 62 on the lower layer contained in the film 6B. In this state,the particles 62 located on the uppermost layer are partially exposedfrom the base material 61 by the abrasive-blasting. Here, the formationof two layers of the particles 62 is not limited only to the case ofstacking the particles 62 in a vertical direction, but instead meansthat the film 6B contains the particles 62 in contact with a lowersurface (a contact surface) of the base material 61, and the particles62 not in contact with the lower surface of the base material 61. Here,it is difficult to form the second layer and so forth according to amethod of spraying the resin material containing the particles.

Here, in the light emitting device 100B, it is possible to form the film6B including several layers to ten layers or more as a consequence ofstacking the adjacent particles 62 by changing the height to flatten thesecond recess of the sealing member 5, or by supplying a resin material,which contains the particles 62 in the highly viscous base material 61,onto the sealing member 5 in the first recess 2 a so as to form a convexprotrusion thereon, for example.

However, the number of stacked layers of the particles 62 in the film 6Bis preferably equal to ten layers or below in order to ensure thetransmission of the light from the light emitting element 1. Here, inthe case where the number of stacked layers of the particles 62 is tenlayers, the first layer preferably has a large proportion of theparticles 62 in contact with the lower surface of the base material 61and each of the second to tenth layers preferably has a large proportionof the particles 62 not in contact with the lower surface of the basematerial 61. In this case, the particles 62 on the first to ninth layersmay be buried in the base material 61 while the particles 62 on thetenth layer may be partially exposed.

A display using the light emitting device 100B according to the secondembodiment as each pixel exerts an antireflection effect, which makes itpossible to reduce the influence of the external light and to favorablyrecognize the brightness and hue of the pixel irrespective of thedirection of observation. Moreover, the light emitting device 100B canalso exert a tackiness prevention effect since at least part of theparticles 62 are exposed from the film 6B to the air. Furthermore, sincetwo or more layers of the particles 62 are stacked in the translucentbase material 61 of the film 6B, the light emitting device 100B canimprove diffusion or reflection of the light from the light emittingelement 1 as compared to the case of disposing one layer of theparticles 62.

EXAMPLES

Next, examples of the present invention will be described.

The light emitting device of the constitution shown in FIG. 1 wasproduced by the above-described manufacturing method. Here, multiplesamples were produced by changing conditions of the abrasive-blasting torender the surface of the film 6 uneven. Shape and Materials of LightEmitting Device

Package 2:

External dimensions in a plan view: 3 mm each side

Opening sizes of sealing member and film: 2.6 mm each side

Lead electrodes 3: Ag plating on surface of Cu alloy

Light shielding member (light reflective member) 4: heat resistantpolymer

Light emitting element 1: mounting one blue LEDSealing member 5:

Base material: silicone resin (refractive index 1.52)

Wavelength conversion substance: YAG phosphor

Film 6 (first film)

Base material 61: silicone resin (refractive index 1.52)

Particles 62: silica (SiO₂) (refractive index 1.46, grain sizes 3 μm to5 μm, content 2% by mass)

Film 6 (second film)

Base material 61: silicone resin (refractive index 1.52)

Particles 62: silica (SiO₂) (refractive index 1.46, grain sizes 8.5 μmto 12.5 μm, content 2% by mass)

The film 6 was formed by mixing the base material 61 made of the sameresin as that used in the base material of the sealing member 5 and theparticles 62 made of silica with toluene, potting the mixture on thesealing member 5 formed in the first recess 2 a of the package 2, andthen drying and curing the mixture. In the meantime, a sample using theparticles 62 having the grain sizes in a range of 3 μm to 5 μm wasproduced as the film 6 (a film coating) and another sample using theparticles 62 having the grain sizes in a range of 8.5 μm to 12.5 μm wasproduced as the film 6 (a second film), respectively.

Conditions of Abrasive-Blasting

Abrasive Liquid (Slurry):

Solvent: purified water

Abrasive: alumina (Al₂O₃) (grain size 3 μm, content 5% by volume)

Blast angles: 30°/90°Blast directions: one direction/two directions in the case of 30°Gun pressures: 0.2/0.3/0.4 (MPa)Machining speed: 40 mm/sec.

The upper surfaces of the samples of the light emitting device wereabrasive-blasted by applying an air pressure to spray the abrasiveliquid from a nozzle as a mist under the above conditions.

In the following, each light emitting device having been provided withthe film 6 and abrasive-blasted will also be referred to as an example,and the light emitting device having been provided with the film 6 butnot abrasive-blasted will also be referred to as a comparative example.

Evaluation

As a consequence of evaluation of characteristics of a comparativeexample, higher light output (light flux) than that before forming thefilm 6 was confirmed. In other words, the light extraction becomesbetter and the light output (the light flux) becomes higher than thecase of not providing the film 6 just by providing the upper surface ofthe sealing member 5 with the film 6 containing the particles 62 havingthe lower refractive index than that of the base material of the sealingmember 5.

The respective samples (examples) produced under different conditions inabrasive-blasting were evaluated for the light output, the lightantireflection effect of the upper surface, occurrence of the fallingoff of the particles 62, and the surface tackiness on the basis of asample without abrasive blasting (the comparative example).

In terms of the external appearance after the machining, the exposure ofthe particles 62 to the machined surface was confirmed in all thesamples subjected to the abrasive-blasting under the various conditions.The higher the pressure at the blast gun was, the more particles 62 wereexposed, and the particles 62 had fallen off the surfaces in somesamples.

As a result of measuring the light output (the light flux) of each ofthe samples, the improvement in the light output (the light flux) wasconfirmed therefrom. Specifically, when the gun pressure was changed foreach sample provided with the film 6 (the first film) using theparticles 62 having the grain sizes in the range of 3 μm to 5 μm, thehighest light output (the light flux) was confirmed in the case wherethe gun pressure was equal to 0.3 MPa. On the other hand, when the gunpressure was changed for each sample provided with the film 6 (thesecond film) using the particles 62 having the grain sizes in the rangeof 8.5 μm to 12.5 μm, the highest light output (the light flux) wasconfirmed in the case where the gun pressure was equal to 0.2 MPa.

Meanwhile, the light output was improved by 0.89% as a consequence ofaveraging the results of the samples provided with the film 6 (the firstfilm) using the particles 62 having the grain sizes in the range of 3 μmto 5 μm. On the other hand, the light output was improved by 0.73% as aconsequence of averaging the results of the samples provided with thefilm 6 (the second film) using the particles 62 having the grain sizesin the range of 8.5 μm to 12.5 μm.

When the blast angle was set to 90°, that is, when the abrasive materialwas jetted at the right angle with respect to the machined surface, itwas confirmed that the amount of exposure of the particles 62 was lessthan that in the case of setting the blast angle to 30°. In themeantime, when the slurry was jetted in one direction while setting theblast angle to 30°, the surfaces of the particles 62 facing the blastdirection were exposed but the surfaces thereof on the opposite sidewere shaded by the particles 62 themselves and were not exposed verymuch. By using the two blasting directions, the amount of exposure ofthe particles 62 was increased. Here, the amount of exposure wasincreased more than that in the case of setting the blast angle equal to90°. This is thought to be because the abrasive material 92 could grindoff the base material 61 more easily as a consequence of setting theblast angle smaller than the right angle.

Moreover, regarding each sample in abrasive-blasting (the example), thepresence of the antireflection effect of the external light as comparedto the sample without abrasive-blasting (the comparative example) wasvisually confirmed.

Furthermore, regarding the sample in abrasive-blasting (example),reduction in tackiness on the upper surface of the film 6 was confirmed.

On the other hand, the effect to prevent the tackiness was not confirmedvery much from the sample without abrasive-blasting (the comparativeexample).

However, the reduction in tackiness was observed after exposing theparticles 62 by abrasive-blasting the comparative example.

The light emitting devices according to the embodiments of the presentdisclosure are applicable to: backlight light sources for liquid crystaldisplays; various lighting devices; large displays; various displaydevices such as advertisement billboards and destination boards; imagereading devices used in apparatuses such as digital video cameras,facsimiles, copiers, and scanners; projector devices; and the like.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A light emitting device comprising: a packagehaving a recess; a light emitting element disposed in the recess; atranslucent sealing material provided in the recess to encapsulate thelight emitting element; and a film provided on the translucent sealingmaterial, the film having a contact surface to contact the translucentsealing material and an outer surface opposite to the contact surface,the film including a translucent base material and two or more layers ofparticles stacked in the translucent base material between the contactsurface and the outer surface, at least one of the particles beingexposed in a vicinity of the outer surface of the film.
 2. The lightemitting device according to claim 1, wherein the translucent sealingmaterial has a substantially curved concave shape viewed in a crosssection including an optical axis of the light emitting element, whereinthe light emitting element is disposed opposite to a center of thesubstantially curved concave shape of the sealing material, and whereina first density of the particles disposed in a vicinity of the center ofthe substantially curved concave shape of the sealing material is higherthan a second density of the particles disposed in a peripheral portionof the substantially curved concave shape of the sealing material. 3.The light emitting device according to claim 2, wherein a first ratio offirst exposed particles to first layered particles is substantiallyequal to a second ratio of second exposed particles to second layeredparticles, the first exposed particles and the first layered particlesbeing disposed in the vicinity of the center of the substantially curvedconcave shape of the sealing material, the second exposed particles andthe second layered particles being disposed in the peripheral portion ofthe substantially curved concave shape of the sealing material.
 4. Thelight emitting device according to claim 1, wherein the at least one ofthe particles is partially exposed.
 5. The light emitting deviceaccording to claim 1, wherein only one side of at least one of theparticles is exposed in a plan view.
 6. The light emitting deviceaccording to claim 1, wherein an upper surface of the translucent basematerial of the film is finely roughened.
 7. The light emitting deviceaccording to claim 1, wherein grain sizes of the particles are in arange from 0.5 μm to 12.5 μm inclusive.
 8. The light emitting deviceaccording to claim 1, wherein on an upper surface of the film, ⅖ or lessof whole sizes of the particles are exposed.
 9. The light emittingdevice according to claim 1, wherein each of the particles in the filmhas a particle refractive index smaller than a base material refractiveindex that the translucent base material of the film has, and wherein adifference between the particle refractive index and the base materialrefractive index is equal to 0.03 or more.
 10. The light emitting deviceaccording to claim 1, wherein each of the particles in the film has aparticle refractive index smaller than a base material refractive indexthat the translucent base material of the film has, and wherein adifference between the particle refractive index and the base materialrefractive index is smaller than a difference between the particlerefractive index and a medium refractive index that a medium at whichlight extracted from the light emitting device is configured to arrivehas.
 11. The light emitting device according to claim 10, wherein themedium is air.
 12. The light emitting device according to claim 1,wherein the particles are made of silica.
 13. The light emitting deviceaccording to claim 1, wherein the translucent base material of the filmcomprises a material selected from an epoxy resin and a silicone resin.14. The light emitting device according to claim 4, wherein the at leastone of the particles located on an uppermost layer is partially exposed.